Around a year ago now, RockShox introduced the Debonair air sleeve for their Monarch line of rear shocks. It features a significantly larger negative spring, as evidenced by the bigger bulge at the shaft end of the air canister. Although many new bikes equipped with Rock Shox suspension are coming with this as standard, you can also retrofit a Debonair sleeve to a 2014 or 2015 Monarch or Monarch Plus shock, and it’ll cost you about $100 to do so. In the grand scheme of suspension upgrades that’s not a lot of cash, but does inexpensive still mean good value?
Before going into details, let’s just quickly recount what a negative spring is and why you might want a bigger one. Taking the damping circuits out of the equation for a minute, with traditional coil sprung suspension your body weight and trail impacts only have to work against the resistance of the steel spring in order to initiate suspension movement. This is why coil suspension has such supple and soft initial feel. Air sprung suspension replaces the coil with a sealed air canister and to stop the air leaking out, the seals have to fit tightly. This snug fit results in seal friction, or ‘stiction’ as it’s more commonly known.
In order to compress or extend your air shock you have to overcome this stiction which is why air shocks have traditionally not been as plush as their coil cousins. This stiction is most obvious on smaller impacts early in the travel. To help overcome this, manufacturers use what’s called a ‘negative spring’; essentially a smaller spring that works against the main spring to help initiate movement.
So here’s the thing; coil-sprung suspension has been around in one form or another for over a century. There’s been plenty of time to figure out how it works best and it’s been fully debugged. Air sprung suspension, at least in its modern format, has only been around for a decade or so. To say it’s in its infancy is probably a bit harsh but it’s certainly not as developed as coil suspension.
The Debonair air sleeve is a radical departure from previous RockShox designs in that the negative spring is proportionally a lot larger. This bigger, and hence more powerful, negative spring works to counteract the inherent stiction of the Monarch shock. As a result it should work more like a coil where you’re only working against the spring force.
More Negative is Positive
In practice it is noticeable. The Monarch Debonair reacts quickly and easily to impacts of all sizes, but especially to small impacts like trail chatter. This lets the rear wheel tracking the ground better and improves traction in all situations. It works so well that the performance difference between air and coil suspension is now very small indeed. On a side note, it’s also worth mentioning that if you don’t use RockShox rear suspension, you can also get a similar setup from Vorsprung’s Corset air sleeve, or from the upcoming Fox 2016 range. Imitation really is the greatest form of flattery.
Before you run off to spend your cash on a new air can, there are a couple of situations where you might not reap any real rewards from a Debonair upgrade. Firstly, some bikes have a dramatically rising rate suspension design; the very high initial leverage ratio works to mechanically overcome stiction in the early part of the shock stroke. With these bikes you may not notice much of a performance difference.
Secondly, heavy riders who run high air pressure might want to think twice. As spring pressure increases, stiction becomes a smaller and smaller proportion of the force resisting shock movement, so any performance gains from the Debonair sleeve will be noticeably smaller. Additionally the bigger negative spring requires more pressure in the positive spring. As an example, I can happily run 120-130psi with a standard air can on my own bike, but getting the same sag with a Debonair can required 160-170psi. If you’re already close to maximum pressure on your old shock, it’s possible you won’t be able to get enough pressure into a Debonair can.
Those two caveats aside, the Debonair air sleeve represents the start of a new era of performance for air shocks. If you’re a light to medium weight rider who wants your bike to stick to the ground over small impacts without needing to run excessive sag, the Debonair air sleeve is about the best $100 suspension upgrade you can possibly find.
Monza Imports
www.monzaimports.com.au
